Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$236.47	10.562%	$261.446	$261.45	$261.45	$261.40
Purchase #2	$144.59	11.776%	$161.6169	$161.62	$161.60	$161.60
Purchase #3	$194.83	3.127%	$200.9223	$200.92	$200.90	$200.90
Purchase #4	$50.60	6.479%	$53.8784	$53.88	$53.90	$53.90
Purchase #5	$140.50	5.684%	$148.486	$148.49	$148.50	$148.50
Purchase #6	$55.35	12.245%	$62.1276	$62.13	$62.15	$62.10
Purchase #7	$66.74	10.140%	$73.5074	$73.51	$73.50	$73.50
7 purchase totals =	$889.08		$961.9846	$962.00	$962.00	$961.90